Battery-operated toothbrushes are known in the art. For example, German Patent No. DE 102 45 086 A1 describes a battery-operated toothbrush including a housing section that is injection molded around a drive unit, or essential parts of the drive unit, thereby fixing the drive unit in place in the housing section. If temperature-sensitive components are used in the drive unit, the thermal effect of injection molding the housing can damage or even destroy the drive unit components.
Moreover, a battery-operated toothbrush that is marketed by the assignee (Braun GmbH) itself is known and is commercially available under the name “Braun Oral-B Cross Action Power.” This battery-operated toothbrush includes a tubular housing, to which a toothbrush head is attached at one end. The other end includes, an opening through which the drive unit, which is attached to a preassembled retaining element (e.g., by clipping) is inserted into the tubular housing section during assembly. Two engaging means are located on the retaining element, which clip into place when the drive unit together with the retaining element is inserted into two pass-through openings formed on the housing part.
The pass-through openings are formed near the opening inside a screw thread, which is disposed on an outer surface of the housing section and adjacent the opening. The screw thread of the housing connects in a torque-proof manner with a corresponding thread of a sealing cap. A replaceable battery, which is electrically connected with the drive unit via contact terminals, is also coupled to the retaining element and in the housing section. When the drive unit is assembled, part of the battery and part of the retaining element, project out of the opening, while the front parts of the drive unit and the retaining element are accommodated in the bore of the housing section.
The tubular housing section is made from plastic and is formed in a tool in an injection molding process. In order to prevent moisture from penetrating the interior of the drive unit via the pass-through openings, the pass-through openings are formed in the thread section, which is enclosed and made waterproof by a sealing cap. An O-ring placed on the thread provides a substantially watertight seal between the sealing cap and the housing section. However, according to this arrangement, the pass-through openings must be locally fixed in the area of the thread on the housing section if they are to remain impermeable to liquid. If the pass-through openings are formed in another location of the housing section and are to remain impermeable to liquid, the pass-through openings must be rendered watertight following insertion of the drive unit in the housing section or must have already been made watertight during the manufacture of the housing section.